Towards the elimination of paediatric tuberculosis in high-income, immigrant-receiving countries: a 25-year conventional and molecular epidemiological case study

Background: The epidemiology of tuberculosis (TB) in high-income countries is increasingly dictated by immigration. The influence of this trend on pediatric TB and TB elimination are not well defined.
Methods: We undertook a 25-year conventional and molecular epidemiologic study of pediatric TB in Alberta, one of four major immigrant-receiving provinces in Canada. All isolates of Mycobacterium tuberculosis were DNA fingerprinted using standard methodology.
Results: Between 1990 and 2014, 176 children aged 0-14 years were diagnosed with TB. Foreign-born children or Canadian-born children of foreign-born parents accounted for an increasingly large proportion of total cases during the study period (from 32.1% to 89.5%). Of the 78 culture-positive cases, 35 (44.9%) had a putative source case identified by conventional epidemiology, 34 (97.1%) with a concordant molecular profile. Of the remaining 43 culturepositive
cases, molecular profiling identified spatially and temporally related sources in 6 cases (14.0%). These 6 children along with 4 other children whose source cases were discovered through reverse contact tracing had a high morbidity and mortality.
Conclusion: The increasing burden of pediatric TB in both foreign-born children and Canadian-born children of foreign-born parents calls for more timely diagnosis of source cases and more targeted screening for latent TB infection.